test-clip: Do not set black/silent by default
audiotransition: Fix porting error of the interpollator

  + update debug statements s/LOG/INFO

(acontrolsource != bcontrolsource)
audiotransition: Add a resampler in the audio transition bin
video-test-src: Force video/x-raw

Avoiding to hit errors with video/x-bayer
basexmlformatter: Do not allow empty file loading
timeline: add auto-transition

API:
 ges_timeline_get_auto_transition
 ges_timeline_set_auto_transition
 GESTimeline::auto-transition
tests: add timeline auto-transition test
tests: add project auto-transition test
clip: Avoid corruption of our list of children while ungrouping
GESAssetLoadingReturn cannot be internal

The enumeration is referenced in a public API.
Update gitignore